MotoAmerica spokesman Paul Carruthers said there were 28 riders in the race and thousands of spectators in the stands when five competitors collided on the first lap. Riders were tossed into the dirt to the side of the track.

The sheriff's office is not investigating the crash at the MotoAmerica Superbike/Superstock 1000 race, which appeared to be an accident, he said.

The track was dry during the race, Carruthers said.

"If there's ever an issue with the track, we don't hold the race," he said.

Carruthers declined to comment on whether MotoAmerica, which organizes the race, will investigate.

MotoAmerica identified the riders killed as 35-year-old Bernat Martinez, 35, of Alberic, Valencia, Spain; and Daniel Rivas Fernandez, 27, of Moana Galicia, Spain. Both were taken to hospitals, where they died.

Track spokesman David Hart said four other riders were treated at the track and released. Their names were not released.

It was not immediately clear what led to the crash, Hart said, adding that Laguna Seca will conduct an investigation.

MotoAmerica president Wayne Rainey sent condolences to the families.

"I really don't have any words to describe what we all feel," Rainey said in a statement. "First and foremost, is the loss to the families and loved ones."